I'm going to do some more testing of hodgdon's published data--when I enter their data into QL it consistently returns pmax of around 10,000 psi or more compared to Hodgdon's pressure ratings. Using even Hodgdon's start loads, with an increased start pressure, I can easily exceed the max pressure rating of 55,000 psi.

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If you’re ever hiking in the woods and you get lost, just look up and find the brightest star in the sky and you’ll know which way space is.I am NOT an expert--I do not have any formal experience or certification in firearms use or testing; use any information I post at your own risk!

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If you’re ever hiking in the woods and you get lost, just look up and find the brightest star in the sky and you’ll know which way space is.I am NOT an expert--I do not have any formal experience or certification in firearms use or testing; use any information I post at your own risk!

I suspected the issue had something to do with total headspace tolerance and the depth of the head to top of the web--the only thing unknown from your measurements is if it is possible that there was some compression due to firing--a possibility at higher pressures.

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If you’re ever hiking in the woods and you get lost, just look up and find the brightest star in the sky and you’ll know which way space is.I am NOT an expert--I do not have any formal experience or certification in firearms use or testing; use any information I post at your own risk!

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If you’re ever hiking in the woods and you get lost, just look up and find the brightest star in the sky and you’ll know which way space is.I am NOT an expert--I do not have any formal experience or certification in firearms use or testing; use any information I post at your own risk!

I've never seen any brass anywhere that comes even close to 1.71--Have you? I'm going crazy trying to figure out why there is such a wide discrepancy between published loads--my loads--and what QL forecasts. I keep coming back over and over to the case failing to seal to the chamber and backing to the bolt breech face before peak pressure is attained.

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If you’re ever hiking in the woods and you get lost, just look up and find the brightest star in the sky and you’ll know which way space is.I am NOT an expert--I do not have any formal experience or certification in firearms use or testing; use any information I post at your own risk!

... case failing to seal to the chamber and backing to
the bolt breech face before peak pressure is attained

Whether the neck expands/locks in forward section, or the case moves back against the bolt face early, or the case seals but stretches to meet the bolt face -- the shorter Starline web appears to be moving back/beyond the protective chamber wall and into the unsupported chamfer space.

That's pretty much the conclusion I came to already, the real question is how to time the cartridge just right so that it has enough pressure quick enough to seal to the chamber and not move back, there's a heck of a lot of tolerance slack involved between the headspace and case lengths. Even if the case support problem goes away, inconsistency in timing will yield inconsistency in performance/accuracy.

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If you’re ever hiking in the woods and you get lost, just look up and find the brightest star in the sky and you’ll know which way space is.I am NOT an expert--I do not have any formal experience or certification in firearms use or testing; use any information I post at your own risk!

One way or another the case head is going to meet the bolt face at those pressures -- stretch or slip.

If you fire some American whitetail 170 interlocs you'll see hornady manages to get the pressure up high enough to keep a good seal to the chamber without going over-board on pressure.

__________________
If you’re ever hiking in the woods and you get lost, just look up and find the brightest star in the sky and you’ll know which way space is.I am NOT an expert--I do not have any formal experience or certification in firearms use or testing; use any information I post at your own risk!

__________________
If you’re ever hiking in the woods and you get lost, just look up and find the brightest star in the sky and you’ll know which way space is.I am NOT an expert--I do not have any formal experience or certification in firearms use or testing; use any information I post at your own risk!

__________________
If you’re ever hiking in the woods and you get lost, just look up and find the brightest star in the sky and you’ll know which way space is.I am NOT an expert--I do not have any formal experience or certification in firearms use or testing; use any information I post at your own risk!

The short web on the starline does sound like a good explanation for the blow out.

However, the extrusion into the ejector hole says there was also an over pressure event. The brass would probably have been "belted" had the entire case wall been fully contained.

All of us 357AR and 350L reloaders are "lab rats" to some extent at this point. I need to go through my brass, find a representative "shortest web" and do something to determine if the case wall is fully contained. Until we better understand the cause of the over pressure events, using cases with walls that are not fully supported is really just plain not smart.

The hornady stuff is pretty pricey, but I have a hundred of those coming in along with 2 hundred winchester cases, should be here tomorrow or Friday. I've noticed a pronounced drop in bolt thrust pressure since I switched to the Faxon BCG--I've removed the heavy spring and H3 buffer and restored conventional carbine weights.

__________________
If you’re ever hiking in the woods and you get lost, just look up and find the brightest star in the sky and you’ll know which way space is.I am NOT an expert--I do not have any formal experience or certification in firearms use or testing; use any information I post at your own risk!

I just went out and did some test firing--the only cartriddge I could duplicate from Hodgdon's data that was also in my QL database is the 147 gr xtp--so I whipped up their lowest load and fired it (using IMR 4227) and for the very first time my velocity results almost matched theirs (even though my barrel is shorter). However, their cartridge specifications essentially will not feed properly in my AR (I doubt anyone else's, either) being far too short with a COL of 2.00".

I'm convinced Hodgdon must have used a bolt gun for their tests. CMMG must have a pretty darn well tuned set-up in their 350 legend AR if they are using the same specs as everyone else--I personally believe it's just not a cartridge design that will work consistently and reliably with as many cartridges in an AR as would work in a bolt gun. To top it off, I finished my shooting session with some handloads in 9mm through my 9mm PCC frankengun cheapo special, and using an unmagnified red dot turned up to around 5MOA I was able to shoot a tighter group than anything I did with my 350 legend and leupold 3x 9 scope. I left pretty disgusted.

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If you’re ever hiking in the woods and you get lost, just look up and find the brightest star in the sky and you’ll know which way space is.I am NOT an expert--I do not have any formal experience or certification in firearms use or testing; use any information I post at your own risk!

Thanks, It is only 50 yds with the 9mm carbine--but with the same scope as is on my legend I'm sure I could beat it at @100 with this particular load--at least at the moment.

This is one of my "Especiale" loads; 65 gr extreme defense @ 2300 fps and over 750 ftlbs energy.

__________________
If you’re ever hiking in the woods and you get lost, just look up and find the brightest star in the sky and you’ll know which way space is.I am NOT an expert--I do not have any formal experience or certification in firearms use or testing; use any information I post at your own risk!

Mehavy--the problem I see with the 350L in an AR is that when you fire it--two projectiles leave going in opposite directions.

__________________
If you’re ever hiking in the woods and you get lost, just look up and find the brightest star in the sky and you’ll know which way space is.I am NOT an expert--I do not have any formal experience or certification in firearms use or testing; use any information I post at your own risk!

I would add for AR's run a patch or two down the bore from the muzzle and stop it just after the lands. Resist the temptation to make the patch too tight fitting--you'll regret it if you do. Make a cone out of paper or other suitable material that fits down into the chamber opening and is high enough and narrow enough to clear the extension lugs but wide enough to fit a metal funnel into. Some people can manage to pour into the chamber and know exactly when to stop before flowing out into the extension without needing a "prevention cone"--I'm not one of them. Heat the cerro over a low flame gradually to get a nice even silvery pool of material and then carefully pour into the chamber with the barrel held vertically (easier if it's in a vice). As soon as you fill the chamber secure your heat sourced tap the plug out with a dowel from the muzzle end within a minute or two--the longer it cools, the more it will expand. It should pop right out easily.

__________________
If you’re ever hiking in the woods and you get lost, just look up and find the brightest star in the sky and you’ll know which way space is.I am NOT an expert--I do not have any formal experience or certification in firearms use or testing; use any information I post at your own risk!

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